The Evolution of the Hubble Sequence

Download or read book The Evolution of the Hubble Sequence written by Rodney Delgado Serrano and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of my thesis was to provide us, for the first time, with a reliable wiev of the distant Hubble sequence, and its evolution over the past 6 Gyr. To achieve this goal, we have created a new morphological classification method which (1) includes all the available observational data, (2) can be easily reproduced, and (3) presents a negligible subjectivity. This method allows us to study homogeneously the morphology of local and distant galaxies, and has the main advantage of presenting a good correlation between the morphological type and dynamical state of each galaxy. The first step has been to study the evolution of galaxies using the IMAGES survey. This survey allowed us to establish the kinematic state of distant galaxies, to study the chemical evolution of galaxies over the past 8 Gyr, and to test important dynamical relations such as the Tully-Fisher relation. The information gained from kinematics is, indeed, crucial to guarantee a robust understanding of the different physical processes leading to the present day Hubble sequence. Using Integral Field Spectroscopy, which provides a complete kinematic diagnosis, we have been able to test our new morphological classification against the kinematic state of each galaxy. We found that the morpho-kinematic correlation is much better using our classification than other morphological classifications. Applying our classification to a representative sample of galaxies at z ∼ 0.6, we found that 4/5 of spiral galaxies are rotating disks, while more than 4/5 peculiar galaxies are not in a dynamical equilibrium. Appliyng our morphological classifications to a repesentative sample of both local and distant galaxies, having equivalent observational data, we obtained a Hubble sequence both in the local and distant Universe. We found that spiral galaxies were 5/2 times less adundant in the past, which is compensated exactly by the strong decrease by a factor 5 of peculiar galaxies, while the fractional number of elliptical and lenticular galaxies remains constant. It strongly suggests that more than half of the present-day spirals had peliculiar morphologies, 6 Gyr ago. Finally, I present further studies concerning the history of individual galaxies at z